1981 C-10 8.5 10 bolt Axle ratio id help please

[GoBraves]

Thanks for letting me join. I feel at home , like a brotherhood of chevy guys! This is ChevyMan Mike. I live in Alabama and love squarebody trucks. I have two C-10. One is a 81 the other 83 1/2 tons. It would be helpful if someone could tell me what axle is installed on my 1981 Chevy C-10. I know it's a 10 bolt 8.5. I looked at some posted threads and didn't see anything that match. The number is a little odd. It looks like TFA on the axle and if so is a 2.56 non- locking. Axle not stamped well, So I'm not sure. Should be three letter all in caps. But the second letter is not a capital letter. Appreciate any input. Thanks

 

[CalSgt]

Chock up a front tire, jack up both rears, spin one tire by hand, if the opposite tire spins the opposite direction it’s Open if spins same direction it’s posi.

If open as suspected, jack only one tire up, put in neutral, mark the driveshaft, and mark the tire, rotate marked tire two full revolutions while counting the rotations of the shaft. 2.5 rotations of the shaft would confirm 2.56:1 ratio Etc.

For posi is same but both tires up and only one rotation of the tire is needed.

With a 40 year old truck there’s no saying what’s actually in the rear end based on the stamps. Too easy for someone to replace the entire carrier and gear set with junkyard parts if the original was ever damaged, not to mention someone changing gears for the heck of it.

Best bet is to pop the cover clean every thing up, look for steel bits in the bottom of the housing & drain oil, inspect the condition of the gear set, identify the carrier type and gear ratio while in there.

 

[Keith Seymore]

You must be registered for see images attach

This this thisity this this.

K

 

[GoBraves]

Thank you for all the great knowledge. This is the direction I will go in.

 

[Corvette Ed]

Welcome aboard from East Tennessee.